In recent years, FPDs (Flat Panel Displays) have been drawing an increasing attention, in place of CRTs (Cathode Ray Tubes). As typical FPDs, a LCD (Liquid Crystal Display) and a PDP (Plasma Display Panel) have been already put into practice. However, it is pointed out that these FPDs have drawbacks explained below.
Since the LCD does not emit light for itself, a high-luminance backlight is required. As a result, electric power consumption tends to increase. The LCD is inferior to the CRT in viewing angle and response speed. On the other hand, the PDP uses a self-luminous element and has a capability which is equal to or higher than that of the CRT in viewing angle and response speed. However, since a high voltage is required to drive the PDP, it is difficult to achieve low electric power consumption in the PDP.
Although the LCD and the PDP have the above mentioned problems, an organic EL device has a potential to solve these problems. For this reason, a display apparatus including the organic EL device has attracted an attention as a candidate of a next-generation FPD.
The organic EL device is typically manufactured in the following method. Initially, an anode is formed over a support substrate such as a cleaned glass, quartz, or plastic, and then is patterned. Typically, as the anode, ITO (Indium Tin Oxide) having a high work function is selected, but other metals may be used. To form the anode, a sputtering process is typically used.
After forming the anode as described above, an organic EL layer (light-emitting layer) is formed. Typically, in a case of a low-molecular organic EL, the organic EL layer is formed by a vacuum evaporation process, while in a case of a polymer organic EL, the organic EL layer is formed by a spin coating process or an ink jet process. The ink jet process is selected when it is necessary to coat different organic EL layers side by side.
To improve a light-emitting efficiency before and after forming the organic EL layer, an interlayer and a hole-injection layer are sometimes formed.
After forming the organic EL layer, a cathode is formed by vacuum evaporation or the like and sealed, thereby completing the organic EL device.
When the organic EL device manufactured as described above is applied to the display apparatus, the organic EL devices are typically arranged in matrix. An apparatus for driving the organic ELs by thin film transistors (TFTs) formed along with the organic EL devices is called an active matrix drive display apparatus, while an apparatus for driving the organic ELs only by electrodes without forming the TFTs is called a passive matrix drive display apparatus.
The active matrix drive has advantages and others that cross talk is extremely less because switching is performed by the TFT provided for each pixel and its life is extended because it is not necessary to emit light with high luminance unlike passive matrix drive. On the other hand, the active matrix drive has a drawback that luminance unevenness occurs due to variations in a threshold and mobility of TFT, etc. For this reason, to implement favorable image display, it is necessary to perform luminance unevenness compensation (initial luminance compensation).
To perform the initial luminance compensation, there is an internal compensation method for compensating for luminance unevenness by performing voltage programming using a programming circuit including the TFT (see, e.g., Patent document 1) and an external compensation method for performing compensation by allowing external memory of a panel to have luminance data (see, e.g., Patent document 2).
In addition to the problem associated with the initial luminance compensation, a problem that a property of the TFT and a property of the organic EL degrade with time will arise. The organic EL device is a DC-drive device. With an increase in a drive time, the property of the TFT and the property of the organic EL degrade, thereby causing luminance unevenness. To solve this, compensation for luminance unevenness (time-lapse luminance compensation) is performed by feeding back a current flowing through the organic EL (see Patent document 3).    Patent document 1: Japanese Laid-Open Patent Application Publication No. 2004-341444    Patent document 2: Japanese Laid-Open Patent Application Publication No. Hei. 9-305146    Patent document 3: Japanese Laid-Open Patent Application Publication No. 2002-278513